The present invention relates to a gas turbine plant with regulated cooling of intake air or compressor air, and also a process for the operation of such a gas turbine plant.
Stationary power stations are used for utility energy supply, and convert, according to constructional type, fossil, nuclear, or regenerative primary sources of energy into electrical current, which is fed into the power network for public or private energy supply. Because of the still unsolved problems in the use of regenerative energy sources (deficient availability, for example for wind power; low efficiency; and also, for nuclear power, the disposal of spent fuel elements), the use of fossil fuel sourcesxe2x80x94coal, petroleum, natural gasxe2x80x94is as always of great importance.
The use of gas turbines fired with natural gas or petroleum is particularly favorable for power generation in power plants. By the consistent use of cogeneration or the use of the arising waste heat as process heat, overall efficiencies of well above 50 percent are attained, which is by far the best value for the use of fossil energy sources. A problem, not to be underestimated, of this kind of plant is that the resulting main data (power and efficiency) have a strong dependence on the ambient temperature. This dependence on the ambient temperature is mostly opposed to the customers"" requirements, in that the plants produce less current with poorer efficiency when the ambient temperatures are high.
Additional necessary protective or control measures can then be superimposed on this basic operating behavior. This is in case, for example, the relatively high temperatures at the compressor end or within the compressor, such as occur due to the high pressure ratios used today, are raised above a limiting value by a high intake temperature. High temperatures at these critical points lead to exceeding the thermal rating of the components there, so that individual component life values given by the manufacturer can no longer be guaranteed.
In the prior art, the temperature is generally limited by reducing the compressor end pressure, and thus the temperature, by suitable means. Since this is above all determined by the absorption capacity of the turbine, suitable measures consist only of a reduction of the intake amount and/or a reduction of secondary introduced material streams (e.g., water or steam into the combustion chamber), and/or a reduction of the inlet temperature into the turbine. All the measures, and also a combination of measures, lead to a further reduction of power and efficiency values of the plant, which diminishes the proper utility of the plant for the proprietor.
The so-called intercooling method is for example known in the prior art, in which the air stream between the booster and the high pressure compressor is cooled in order to reduce the temperature of the intake air. The cooling can take place here by means of heat exchangers or by injecting a cooling medium, e.g., water.
Thus, e.g., U.S. Pat. No. 6,012,279 describes such a process for the cooling of the partially compressed air between the low pressure compressor and the high pressure compressor by injecting water. This injection has the result that both the temperature of the air stream leaving the high pressure compressor, and also the temperature in the combustion chamber, are reduced.
U.S. Pat. No. 5,463,873 furthermore describes the evaporative cooling of the intake air of a gas turbine, in which the amount of the injected water is adjusted so that the saturation limit of water in the air stream of the turbine is not exceeded. Since such an injection cooling normally uses deionized water, which is expensive, for the protection of the gas turbine, the control is directed to avoiding condensation of water in the gas turbine in order to keep the costs low, and on the other hand, to keeping the pressure drop of the intake air to a minimum value, instead of injecting the optimum amount of water.
The invention is directed to a gas turbine plant, in particular a gas turbine power plant, a combined heat and power plant, or a cogeneration plant, with at least one compressor compressing intake air, at least one component heating the intake air compressed by the compressor, which component is in particular a combustion chamber or a catalyst, at least one turbine using as a working medium the hot air from the component for heat supply, and at least one generator coupled to the gas turbine, wherein cooling means are present which permit the cooling of at least a portion of the intake air and/or a portion of partially compressed intake air within the at least one compressor. The invention is also directed to a process for the operation of the above-described system. The invention ensures that the thermal rating of components at critical places in the air path of the gas turbine are not exceeded, and that simultaneously a cooling medium is used for the cooling of the intake air stream or else the air stream within the compressor or between different stages of compression. The system is operated as economically and optimally as possible, both in relation to the external conditions and also in relation to the internal gas turbine process.
U.S. Pat. No. 6,012,279 cannot achieve the results of this invention since the use of intercooling, or respectively the injection of water into the intake air path, or both in combination, is described without explaining how this injection or cooling is to be optimally effected in relation to external and also internal conditions.
U.S. Pat. No. 5,463,873 cannot achieve the results of this invention since only the adjustment of the injection to the saturation value in the intake air path is described, i.e., a control which regulates the injection to a value which is below the saturation limit of water in the working medium path.
The desired results are achieved by the present invention since the cooling means is designed such that under the usual conditions it is capable of cooling the intake air path of the gas turbine to the extent that critical temperature values at critical places are not exceeded; and the cooling means is directly driven in a controlled manner at critical places in dependence on the temperature values.
The invention is directed to a gas turbine plant in which the cooling means is suitable for cooling at least a portion of the air mass flow before or within the compressor such that the air temperature and/or component temperature at critical places does not exceed a prescribed maximum temperature predetermined by the component materials arranged at the critical places, and such that temperature measuring devices are arranged in the location of at least one of the critical places, their temperature measurements being used for specific regulation or control of the cooling means.
The invention thus provides a specific control of the cooling means. The control is optimized so that effectively the actual temperature values arising at the critical places are measured and used as control parameters. It is thus ensured that the cooling means is used only in the exactly necessary effective amount, i.e., only in relation to the extent actually required at the critical places. The use of the cooling means is minimized in this manner, or respectively the reduction of the overall efficiency of the gas turbine plant due to the cooling is kept to the minimum required value.
A first preferred embodiment of the gas turbine plant according to the invention is characterized in that for the specific regulation or control of the cooling means, it is not the temperature at one of the critical places which is measured, but another measurable quantity of the gas turbine process which represents an indirect measure of the prescribed maximum temperature value in the location of at least one of the critical places. In other words, it is also possible not to measure the temperature directly at the critical place, but to take another process value instead, which process value is however a determinable function of the temperature value at at least one of the critical places.
A further preferred embodiment has a low pressure compressor and a high pressure compressor, and preferably at least a portion of the partially compressed intake air issuing from the low pressure compressor is cooled by the cooling means. Furthermore the cooling means is preferably capable of sufficiently cooling the whole of the partially compressed intake air. The cooling means can however also or additionally be designed such that the whole of the intake air can be cooled.
A further preferred embodiment has, in addition, at least one waste heat boiler and furthermore, particularly preferred, at least one steam turbine, the waste heat boiler producing steam for operating the steam turbine from the hot exhaust gases leaving the gas turbine, and particularly preferred, with the gas turbine, generator and steam turbine all mounted on a common shaft. The above construction can, in other words, be useful for so-called single-shaft plants.
The cooling means can be provided in very different forms. On the one hand it is conceivable to provide a heat exchanger through which a cooled medium flows, the temperature of the coolant in or at the heat exchanger and/or the amount of the cooling medium being regulated by the heat exchanger for the limitation of the measured, predetermined temperature. However it is also possible to provide a surface-wetted evaporative cooler, the amount of water conducted over the surface of the cooler being controlled for the limitation of the measured temperature. Or there can be provided, alternatively or additionally, at least one nozzle as the cooling means, with which water or another suitable liquid, or else a liquid mixture, can be sprayed in in a finely divided state. In this case, the amount of water or liquid sprayed in by means of the nozzles can be controlled for the limitation of the measured temperature. Then particularly preferred, additionally to the cooling effect by evaporation, a temperature-reducing effect, which increases efficiency, of a wet cleaning of the compressor blades during operation can in addition be used regularly or even permanently, in that more water is regularly or permanently sprayed in intentionally than corresponds to the saturation limit of the air.
The following regions within the gas turbine plant are concerned, preferably but not exclusively, as the critical places: at the end of the compressor, in the compressor diffuser, in the plenum before entry into the first combustion chamber, at a place within the compressor, at an air bleeding place of the compressor, in the cooling system for turbine cooling, at the metal of the rotor, at the metal of the gas turbine housing, at the metal of the compressor blades, at the metal of the components of the combustion chamber. The compressor outlet is found to be particularly critical.
Furthermore, the present invention relates to a process for the operation of a gas turbine plant, as described hereinabove. In particular, in such a process, the temperature values measured at the critical places in such a process are supplied to a control unit (usually a computer) which in its turn then controls the cooling means. The control is in particular arranged such that the measurement assumes control which first reaches the maximum value allotted to it. Furthermore, the controlling means is preferably adjusted so that the cooling means is already controlled at a certain spacing, i.e., beneath the maximum value.
A particularly preferred embodiment of the process is characterized in that leading quantities are calculated indirectly from at least one, or from a combination, of several measurement values, particularly preferred in that the temperature is determined by a measurement of the compressor end pressure or intermediate pressure, if necessary in addition taking the ambient temperature into account, or in that the position of at least one adjustable compressor front guide row is used, if necessary taking additional account of the ambient temperature, in order to determine the operating state, i.e., a temperature estimation of the critical places.